Direction finder



DIRECTION FINDER Filed Aug. 10, 1945 llm RECEIVER TO RECEIVER RECEIVER INVENTOR HERBERT G. CARTER Z L).- AM

ATTORNEY Patented Feb. 8, 1949 UN l T E-D STATES T OFFICE DIRECTION FINDER Herbert G. Carter, Dayton, Ohio 7 Application August 10, 1945, Serial No. $10,179 "Clain'ms. (Cl. 250-333?) (Granted under the act ofMarch 3, 1883-, as

amended April 30, 1928; 370 '0. G. 757

The invention described herein may be manufactured and used by or for the Government for governmental purposes, "without the payment to me of any royalty thereon.

This invention relates to electrical apparatus and more particularly to directional radio antennas. I

Conventional loop antennas are known to have directional receiving properties, that is, the sigrial supplied to a receiver by the antenna is a maximum when the source of received signals lies in the plane of the loop, and the signal supplied by the antennais a minimum when the axis of the loop is directed at the source of the received signals. It is also known that the usefulne'ss of the conventional loop antenna is limited by the fact that the receiving sensitivity pattern of the antenna is symmetrical about both the plane of the loop and the axis of the loop and that two no-si'gnal or null points exist in the receiving pattern. When loop antenna is directed :so that the signal is reduced to zero or a minimum, it is then known that the source of the received signal lies along the axis of the loop, but it is impossible to tell on which side of the loop the station lies. Combinationsof the conventional'loop antenna with other directional and nondire'ctional antennash'ave been used to determine the true location of the signal source. These combinations usually require the mixing of the signals from two or more antennas with the consequent complexity of circuits involved. The accuracy of these systems also depend-sto a large degree on the careful adjustment of the circuits and the proper proportioning of the signal strengths of the various antennas.

It 'iswan object of the present invention',there fore, to provide a loop antenna, hereinafter called the Carter-loop antenna, that has a single no-signal or null point in the complete 360- degree field pattern about the antenna.

It is a further object of this invention to provide means including a single loop antenna and associated receiver circuit for locating a source of radio-frequency signals.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings in which:

Fig. l is a sectional view of a conventional loop antenna;

Fig. 2 is the directional receiving pattern of the antenna of Fig. 1;

Fig. 3 is -a sectional v'iewof the present invention; I

Fig. 4 is a front view of the invention;

Fig. 5 is a directional receiving pattern afforded by the present invention; and

Fig. 6 is aschematic view showing one applic'a tion of the present invention.

mIhe disadvantages of conventional loop-an; tennas may be more 'f-ully understood by considering Figs. 1 and -2. The loop antenna 8 of Fig. 1 consists of a form I0 on which a continuous conductor is wound in "several turns forming one or more uniform layers. In this exam-'- ple asingle layer of turns 4'2 is shown. The two ends of the conductor that lswound on form 10 are connected through. a shielded cable H to a receiver (not shown). The amplitude "of th'esignal supplied by this antenna to the receiver as a funct ion'o f angular positionis illustrated in' Fig, 2. A plan view of antenna'B is shown "as a reference. The distance from the center point 16 of antenna 8"130 the two c'urveslB and 20 is propo'rtional to the intensity of signal supplied by antenna 18 to the receiver as a unit signal source is moved in a circle about point l6,"the. distance in all cases-being measured in the direction of the signal "source. It can be seen from Fig; "2 that two no-signal or null points exist when the signal source is in the directions indicate'cl'by lines 22 and 24. Lines 22 and '24 are coincident with the axis of the turns wound on form 10. This axis is hereinafter called the loop axis." If antenna 8 is employed the normal manner, that is, is rotated "about a vertical "axis passing through point [6 to locate a fixed source of signals, it would be impossible to determine whether the source of the signal came from the direction of line 22 orfline 24.

Referring now to Fig. 3 where there is show nza sectional view of a one-null or Carter-loop antenna 30, the structure includes a dielectric or plastic form 32 identical with or similar to the form I0 shown in Fig. 1. The windings 34 on form 32 are formed from a single conductor but the turns are not wound in uniform layers as was the case in Fig. 1; rather they are wound in the form of a so-called banked winding. In this case the left edge of the winding 34 consists of only a single layer of turns while near the right edge winding 34 consists of four layers of turns. Each turn of the winding is insulated from all other turns by employing enameled covered wire or by placing some form of insulating material between adjacent turns. In this embodiment of the invention the first alternative is Fig. 4 shows a front view of antenna 30, cable; 36 and receiver 38 being schematically shown as before. Parts in Fig. 4 are numbered to 'corres be established so that the operator in airplane 60 may locate his position by triangulation. Obviously the example given above is only one of many applications of this invention.

While there has been described what is at present-considered the preierred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications ;may be made therein without departing from the spond with like parts in Fig. 3.

The directional receiving propertiesof invention are illustrated by Fig. In Fig 5 the a constant signal sourceis moved in acircle about i point 42, the distancelibeing measured at all timesin thedirection of the signal source;

It can be seen that curve 40 dips very sharply in the directionof line 46,1 line 46 lying along the loop axis of antenna -39. Aslight decrease in signal occurs in the direction of. line 48 which also lies along the loop axis of antenna 30,-'but this slight decreasein signal may-be easily differ.- entiated from the decrease in-signal in the direction of line 46. The, 'nonsymmetrlcal receiving sensitivity pattern is due to the fact that the antenna supplies a, much stronger signal'to the receiver when the banked side of the winding is nearer the signal source .than is supplied when the low side of the winding (in thisexample the side having onlyia single layer of turns) is nearer the signal, source.- LineAB therefore lies on the banked side of winding .34.

."The use of this antenna as-a direction'finder is apparent "from a study of the above description. Antenna 3;!) is mounted so that it may be rotated about a vertical' axis passing through point 42 and perpendicular to the loop axis of theantenna. When a signalis received, antenna 3G is rotated about t his.vertical axis until a very sharp decrease in signal: occurs. When'the antenn'a'is rotated to the no-signalposition, the source of received signals will lie on the line that is a. prolongation of the loop axis of the antenna and on the side. of theantennathat has themos't layersin the winding. -An application of'jthisantenna is shown in Fig. 6. An ai plane 60 equipped with a'Carter-loop antenna 62 receives signals from a radio transmitter E4. The antenna 6'2 on airplane 6B is now rotated to the'n'o-signal position. The station 64- is identified by the radio operator in airplane B0, and a line of position from the known location of the station to'airplane 63 is established. The airplane 6U may home on station 64 or a line of position to a second station (not shown) may antenna comprising a dielectric means, a' continuous conductor having a first invention.

What is claimed is:

1. In combination with a receiver, a directional supporting portion .helically wound in a plurality of turns on said supporting means and a second portion coaxiall'y wound on said first portion in a plurality of turns forming a plurality of layers banked at one end of said supporting means, each of said turns being electrically insulated from the others, and a shielded cable connecting the ends or" said conductor tosaid receiver.

2. In combination with a receiver, a directional antenna comprising a. dielectric supporting means, a continuous conductor having a first portion wound in a plurality of turns on said'sup' porting means, and a second portion .wound on said first portion in a plurality of turns forming banked layers at one'end of said supporting means, and a shielded cable connecting the ends of said conductor to said receiver. r 3. In combination with areceiver, a directional antenna comprising a continuous conductor having a. first portion wound in a plurality of turns forming a helix and a second'portion wound on said first portion in a plurality of turns forming a plurality of banked layers at one end of said helix, and a shielded cable connecting the ends of said conductor to said receiver.

4. A directional antenna comprising a continuous conductor having a first portion wound in a plurality of turns forming a helix and a second portion wound on said first portion in. a plurality of turns forming layers unequally distributed along said first'por'tion to provide for sense de termination of the source of energy induced in said antenna.

' 5. A directional antenna as set forth in claim 4, wherein the layers arebanked. p

' HERBERT G. CARTER.

REFERENCES CITED Thevfollowing references are of record in the file of this patent:

UNITED STATESVIPATENTS Number Name Date 2,383,415 Polydoroff Aug. 21, 1945 

